1. Field of the Invention
The present invention relates to a rolling guide apparatus having light-weight and high-rigidity and is applicable to a linear guide apparatus such as a machine tool or an X-Y table.
2. Description of the Related Art
A rolling guide apparatusxe2x80x94which is incorporated in a machine tool or the like and guides a table for carrying a workpiecexe2x80x94comprises a race shaft in which a rolling element rolling surface is formed in a longitudinal direction thereof; and a sliding table which has an endless circulation passage including a load rolling surface corresponding to the rolling element rolling surface and is attached to the race shaft via a plurality of rolling elements housed in the endless circulation passage. The race shaft and the sliding table are movable relatively to each other by means of rolling elements.
The sliding table comprises a sliding table main body in which the load rolling surface and a rolling element return passage substantially parallel to the load rolling surface are formed; and side covers in which changing direction passages for connecting both ends of the load rolling passage and the rolling element return passages and which are attached to respective ends of the sliding table main body.
Studies on such a rolling guide apparatus have been examined for the purpose of making the sliding table light-weight, reducing inertia force, and enabling high-speed start and stop operations. Rolling guide apparatus described in Japanese Patent Application Laid-Open Nos. 219520/1984 and 219153/1996 has a sliding table main unit, wherein the sliding table main unit except a load rolling surface is made from synthetic resin.
Studies on the load rolling surface of the sliding table main body have been examined for improving rolling fatigue strength and abrasion resistance against rolling elements. Japanese Patent Application Laid-Open No. 325414/1998 discloses forming guide surfaces of a sliding table or the entirety of the sliding table from ceramic to prevent generation of waste, which would otherwise be caused when rolling elements come into contact with the rolling element rolling surface.
Demand exists for a sliding table main unit having superior mechanical characteristics such as flexural strength, and easy to be machined. The sliding table main unit made from synthetic resin except the load rolling surface is easy to be machined but not necessarily superior in terms of mechanical characteristics.
Even in case where the load rolling surface is made from ceramic to prevent generation of waste, the rolling fatigue strength and abrasion resistance against rolling elements are not enough.
The present invention provides a rolling guide apparatus applicable to a linear guide apparatus such as a machine tool or an X-Y table, and particularly, a light-weight and high-rigidity rolling guide apparatus achieved by compounding of ceramic raw material.
According to a first aspect of the present invention, there is provided a rolling guide apparatus comprising: a race shaft having a rolling element rolling surface formed in a longitudinal direction thereof; a sliding table having an endless circulation passage including a load rolling surface corresponding to the rolling element rolling surface, the sliding table being movable relatively to the race shaft; and a plurality of rolling elements being housed in the endless circulation passage so as to circulate in accordance with relative movement of the race shaft and the sliding table, wherein the sliding table comprises: a sliding table main unit having the load rolling surface and a rolling element return passage substantially parallel to the load rolling surface; and side covers each having a changing direction passage for connecting ends of the load rolling surface and the rolling element return passage, the side covers being attached to respective ends of the sliding table main unit, and wherein the sliding table main unit comprises: a load rolling surface section made from engineering ceramic and having the load rolling surface; and a main body section made from machinable ceramic.
According to the first aspect, the load rolling surface section having the load rolling surface is made from engineering ceramic having superior rolling fatigue strength and superior abrasion resistance. The main body section which is the rest portion of the sliding table main unit is made from machinable ceramic having a superior mechanical characteristic and is easy to machine. Thus, the sliding table main unit fulfills the characteristics that have been required hitherto and accomplish weight reduction and high rigidity. Hence, high-speed start and stop operations with small inertia force is realized.
According to a second aspect of the present invention, the rolling guide apparatus further comprises: a race housing groove being formed in the main body section; and a bearing race serving as the load rolling surface section, the bearing race being fitted into the race housing groove.
According to the second aspect, the race housing groove can be readily formed in the main body section made from machinable ceramic having ease of machining. Hence, a bearing race which has superior rolling fatigue strength and acts as a load rolling surface section can be readily fitted into the race housing groove. The bearing race is made from engineering ceramic having superior rolling fatigue strength. Hence, there can be achieved a long-life rolling guide apparatus.
According to a third aspect of the present invention, the race housing groove and the bearing race have semi-circular cross-sectional profiles which complement each other, the bearing race is rotatable with respect to the race housing groove.
According to the third aspect, the race housing groove and the bearing race have semi-circular cross-sectional profiles which complement each other, and the race housing groove and the bearing race are formed so as to be rotatable. Hence, self aligning operation can be effected.